[brycebb]

One question states this.
Determine the formal charge of oxygen in the following structure. If the atom is formally neutral, indicate a charge of zero. CH3O
The structure is a carbon with two single bonds to hydrogen, a double bond with oxygen, and the oxygen has a single bond with a hydrogen atom and the oxygen has a lone pair of electrons. Since this oxygen atom only has 5 electrons in the compound, the formal charge is +1. I got that part right. Now the second part states this
Draw an alternative Lewis structure for the compound given in part (a). Show the unshared pairs and nonzero formal charges in your structure. Don\'t use radicals.
Now what I drew had carbon having 3 single bonds with hydrogen atoms and a single bond with the oxygen atom, and the oxygen atom having 3 lone pairs and a formal charge of -1. However, this is the wrong answer and I do not understand why, can someone help me?
 

[Dan]

Have a look around for information about drawing resonance forms.

Example: http://chemistry.umeche.maine.edu/CHY251/Reson.html

Basically, you need to keep track of your electrons.

In your first structure, the O has 3 bonds and one lone pair, 8 electrons, fine. The C has 4 bonds, 8 electrons, also fine.

In your second structure, you have an O with two bonds and 3 lone pairs - that's 10 electrons, remember the octet rule. The C has 3 bonds and no lone pairs, 6 electrons, also breaks octet rule.

Also - these are not constitutional isomers, the atom connectivity is the same in both structures.